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111.
112.
A detailed analysis of the gas phase pyrolysis of 1,4-dithiaspiro[4,4]nonane(I), 1,5-dithiaspiro(5.4)decane(II), 1,4-dithiaspiro(4.5)decane(III), and 1,5-(5,5)undecane(IV) is presented. Pyrolysis resulted primarily in cleavage of the molecules to thiocyclopentanone and thiocyclohexanone. The products observed are discussed in relation to the effect of ring size in cyclic dithioketals. A definite correlation was noted between the thermal and their electron-impact-induced fragmentations of these materials. 相似文献
113.
Wollastonite glass-ceramics were prepared through pressureless sintering. The sinterability of the prepared samples of the glassy powder in the system (SiO2-CaO-Na2O-Fe2O3-WO3) was investigated in the temperature range 720-900 °C and soaking time of 180 min. The influence of the increase in the glass powder particle size on the sinterability and dielectric properties of the glass-ceramic samples was studied.The sintered specimens were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. XRD analysis revealed that wollastonite was the main crystalline phase in the sintered glass-ceramics. Dielectric properties such as dielectric constant and dielectric loss were measured via a network analyzer at 10 GHz.It was observed that the increase of the glassy powder particle size improved the sinterability and dielectric properties of the glass-ceramic specimens. Wollastonite glass-ceramics with 16 μm particle size had maximum constant and minimum loss (εr = 10.10 and tan δ = 0.005) compared with the other glass-ceramics. 相似文献
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115.
The high-energy current of runaway electrons during a major disruption in tokamak reactors can cause serious damage to the first wall of the reactors and reduce their life time. Therefore, finding a method to minimize runaway electron generation during a major disruption is much needed. Tokamak limiter biasing is one of the methods that can be used for controlling the radial electric field and can induce a transition to an improved confinement state. This paper attempts to examine the effect of limiter biasing on the generation of runaway electrons during a major disruption. To do so, a horizontal biased limiter placed on the tokamak was used. Main parameters such as plasma current, loop voltage, emitted hard X-ray intensity, magnetohydrodynamic (MHD) oscillation and Hα radiation and spectrum of hard X-rays, in the presence and absence of negative and positive limiter biasing, were measured. The results show that the application of limiter biasing during a major disruption can reduce runaway electron generation. 相似文献
116.
Fatemeh Mohammadi 《代数通讯》2013,41(10):3753-3764
In this article, Cohen–Macaulay chordal graphs and generalized star graphs are studied to show that all powers of the vertex cover ideal of such graphs have linear quotients. Moreover, it is shown that the Alexander dual of the clique complex of any chordal graph is vertex decomposable. 相似文献
117.
H. Bidadi S. Mohammadi Aref M. Ghafouri M. Parhizkar A. Olad 《Current Applied Physics》2013,13(2):355-359
A composition of GaAs-polymer tiny particles was pressed at a temperature of 130 °C and a pressure of 60 MPa and its current–voltage characteristic was studied. The result shows that the prepared disk has varistor behavior and can therefore be used to protect circuits from low overvoltage transients higher than 62 V. Temperature dependence of current-voltage characteristic and the electrical conductivity of the sample were investigated in the temperature range of 25–100 °C. It has been found that increase in temperature results in lower breakdown voltage and nonlinearity coefficient. At high temperatures, nonlinearity in the I–V characteristic of sample disappears and the conductivity becomes Ohmic in nature. The sample has hysteresis which decreases through increase in temperature. Annealing effect on leakage current and breakdown voltage was both investigated and analyzed using SEM micrographs. Finally, the electrical bandgap of the sample was measured. 相似文献
118.
The Weibull distribution is widely used in applications such as reliability and lifetime studies. Although this distribution has three parameters, for simplicity, literature pertaining to Weibull parameter estimation relaxes one of its parameters in order to estimate the other two. When the three-parameter Weibull distribution is of interest, the estimation procedure is complicated. For example, the likelihood function for a three-parameter Weibull distribution is hard to maximize. In this paper, a Cross Entropy (CE) method is developed in the context of maximum likelihood estimation (MLE) of a three-parameter Weibull distribution. Performing a simulation study, a comparative analysis between the newly developed method and two existing methods is conducted. The results show the proposed method has better performance in terms of accuracy, precision and run time for different parameter settings and sample sizes. 相似文献
119.
Bahareh Feyzi Barnaji Hamid Salehzadeh Behzad Darbasizadeh Rassoul Dinarvand Abdollah Salimi Ali Mohammadi 《Electroanalysis》2019,31(9):1719-1727
In the present work, the oxidation of acetaminophen in the absence and presence of eflornithine was electrochemically investigated by means of cyclic voltammetry at a glassy carbon electrode (GCE). Our results indicate that N‐acetyl‐p‐benzoquinone imine (NAPQI) produced from two‐electron electrochemical oxidation of acetaminophen participates in a Michael addition reaction with eflornithine via an ECE mechanism. This fact was used for the determination of eflornithine using differential pulse voltammetry (DPV) technique on the surface of β‐Cyclodextrin modified glassy carbon (β‐CD/GC) electrode. β‐CD/GC electrode was prepared through an electrodeposition procedure and characterized by Fourier‐transform infrared spectroscopy (FT‐IR), Cyclic Voltammetry (CV), Field Emission Scanning Electron Microscopy (FESEM) and Energy‐dispersive X‐ray spectroscopy (EDS) techniques. Under optimum conditions, the β‐CD/GC electrode showed a good linearity as a function of the eflornithine concentration over the range from 5 to 100 μM with detection limit and quantification limit of 1.94 and 5.8 μM, respectively. Finally, the proposed protocol was confirmed to be successful in determination of eflornithine in human urine samples with good recovery, ranging from 97.2 % to 104.8 %. 相似文献
120.
Mohammadreza Mohammadi Nilash Fahimeh Mirzaei Ali Reza Fakhari 《Journal of separation science》2019,42(9):1786-1793
A new sample preparation method based on SBA‐15 assisted electromembrane extraction coupled with corona discharge ion mobility spectrometer was developed for the determination of Thiabendazole as a model basic pesticide in fruit juice samples. The addition of SBA‐15 in the supported liquid membrane in electromembrane extraction system not only can lead to enhancement of the effective surface area, but also introducing the negatively charged silanol groups into supported liquid membrane might improve migration of positively charged analytes toward the supported liquid membrane and finally into the acceptor solution. To investigate the effect of the presence of SBA‐15 in the supported liquid membrane on the extraction efficiency, a comparative study was carried out between the conventional electromembrane extraction and SBA‐15/electromembrane extraction methods. Under the optimized conditions, SBA‐15/electromembrane extraction method showed higher extraction efficiencies in comparison with conventional electromembrane extraction method. SBA‐15/electromembrane extraction method exhibited a low limit of detection (0.9 ng/mL), high preconcentration factor (167) and high recovery (83%). Finally, the applicability of SBA‐15/electromembrane extraction method was studied by the extraction and determination of Thiabendazole as a model basic pesticide in fruit juice samples. 相似文献